This invention relates generally to aircraft ventilation systems and, more specifically, ventilation systems for air crew and flight attendant rest areas.
Many commercial airline flights travel a great enough distance and for a long enough duration that crew rest is required. Because of the need for adequate rest facilities for the flight crew and cabin crew members, rest areas are sometimes provided within the aircraft for use by the crew members while the aircraft is in flight or on the ground. In many cases, the rest areas are relatively small, such as single person units remotely located in the vicinity of the aircraft""s cockpit. In other aircraft, flight crew rest areas are created in an overhead crown area, above the passenger seating area.
Ventilation systems in the rest areas are typically tied directly into the aircraft""s main ventilation system. Obtaining and maintaining a habitable environment within the rest areas and complying with safety regulations has been a problem due to a number of factors, including a relatively large size of the main ventilation system of the aircraft, wide ranging atmospheric environmental conditions, the relatively small size of the rest areas, and the location of the rest areas in remote parts within the aircraft.
Cool air pulled from the aircraft""s main air conditioning pack is often excessively cold for relatively small rest areas. If the aircraft""s main ventilation system is continually running, the rest area is too cold to occupy until the rest area can be adequately heated. Conversely, if the ventilation system is shut down for any appreciable length of time, especially in warmer climates, the rest areas can become too hot to occupy. In either case, the rest areas and the items within the rest area represent a thermal mass that increases the time required to heat or cool the space to a habitable level. This additional uninhabitable period reduces the amount of time a crew member can rest, potentially preventing some crew members from receiving enough rest.
Another problem with pulling air directly from the main air conditioning pack is the adverse effect on ventilation system components. More specifically, under certain atmospheric conditions, such as those encountered on the ground or in flight below 25,000 feet, icing can occur in the ventilation system. Icing is particularly likely under warn, humid conditions in which moist air drawn from outside the aircraft is cooled and freezes within the ductwork. Icing can detrimentally affect operation of shut-off valves and other components downstream from the air conditioning packs, creating an undesirable or uncertifiable ventilation condition. Frozen valves are particularly troublesome when the valves operate a system to exhaust smoke from the cabin.
Therefore, there is a need for a system for maintaining habitable conditions in aircraft crew rest areas during all phases of flight, including ground operations and taxi, takeoff, and landing.
The preferred form of the present invention incorporates a pressure sensor in line with the main overhead flight crew rest air supply line. The pressure sensor provides information to the environmental control system regarding the amount of air flowing through the main supply line. If air pressure decreases because of ice build-up, a failed supply valve, a ruptured supply duct, or any other reason, it will be detected by the pressure sensor. In the event the pressure drops below a desired level, the environmental control system opens a valve on a secondary air supply line.
In accordance with other preferred aspects of the invention, the air temperature from the air packs is maintained below 40 degrees F. so that only heaters are required downstream to obtain the desired air temperature. Air conditioning is not required, thereby reducing the likelihood of icing and simplifying the overall configuration.
The invention also preferably includes provisions for smoke detection and exhaust, fault detection and maintenance, and other features.